Chapters on the scrubber, Skip OP/ED, audio/subtitle menus

- PlaybackController exposes chapters, segments (Jellyfin
  MediaSegments for account holders), tracks, position/duration.
- Own seek bar with chapter diamonds and chapter title on hover,
  seeking through the sync user-seek path.
- Skip OP / Skip ED pills from Intro/Outro segments or chapter names
  (ED skips to its end only); Skip 1:30 fallback for >20 min videos
  without OP info; next-episode pill now starts at the ED.
- PgUp/PgDn chapters, Shift+Right +1:30; Audio and Subtitles menus
  with count badges via the existing track path.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/core/lib/src/jellyfin/client.dart

@@ -499,6 +499,27 @@ class JellyfinClient {
   Map<String, String> get authHeaders =>
       {'Authorization': clientInfo.authorizationHeader(accessToken)};
 
+  /// `GET /MediaSegments/{itemId}` (Jellyfin 10.10+): the item's intro,
+  /// outro, recap, preview and commercial ranges, in start order. Empty when
+  /// no segment provider has marked it, and on servers without the
+  /// endpoint (404).
+  Future<List<JellyfinMediaSegment>> mediaSegments(String itemId) async {
+    final Object? j;
+    try {
+      j = await _json('GET', '/MediaSegments/$itemId');
+    } on JellyfinException catch (e) {
+      if (e.statusCode == 404) return const [];
+      rethrow;
+    }
+    final items = _map(j)['Items'];
+    final list = [
+      if (items is List)
+        for (final e in items)
+          if (e is Map) JellyfinMediaSegment.fromJson(e.cast<String, dynamic>())
+    ]..sort((a, b) => a.startTicks.compareTo(b.startTicks));
+    return list;
+  }
+
   // ------------------------------------------------------------ progress
 
   /// `POST /Sessions/Playing`: playback started (Jellyfin shows the session

packages/core/lib/src/jellyfin/models.dart

@@ -555,3 +555,54 @@ class JellyfinPlaybackInfo {
     return mediaSources.isEmpty ? null : mediaSources.first;
   }
 }
+
+/// Kind of a [JellyfinMediaSegment] (Jellyfin `MediaSegmentType`).
+enum JellyfinSegmentType {
+  unknown,
+  commercial,
+  preview,
+  recap,
+  outro,
+  intro;
+
+  static JellyfinSegmentType parse(String? v) => switch (v) {
+        'Commercial' => commercial,
+        'Preview' => preview,
+        'Recap' => recap,
+        'Outro' => outro,
+        'Intro' => intro,
+        _ => unknown,
+      };
+}
+
+/// A marked range of an item (`GET /MediaSegments/{itemId}`, Jellyfin
+/// 10.10+): intro, outro, recap, preview or commercial. Filled by segment
+/// provider plugins; without one the list is empty.
+class JellyfinMediaSegment {
+  final String id;
+  final String itemId;
+  final JellyfinSegmentType type;
+  final int startTicks;
+  final int endTicks;
+  const JellyfinMediaSegment({
+    required this.id,
+    required this.itemId,
+    required this.type,
+    required this.startTicks,
+    required this.endTicks,
+  });
+
+  Duration get start => ticksToDuration(startTicks);
+  Duration get end => ticksToDuration(endTicks);
+
+  factory JellyfinMediaSegment.fromJson(JellyfinJson j) => JellyfinMediaSegment(
+        id: _str(j['Id']) ?? '',
+        itemId: _str(j['ItemId']) ?? '',
+        type: JellyfinSegmentType.parse(_str(j['Type'])),
+        startTicks: _int(j['StartTicks']) ?? 0,
+        endTicks: _int(j['EndTicks']) ?? 0,
+      );
+
+  @override
+  String toString() => 'JellyfinMediaSegment(${type.name} $start-$end)';
+}

packages/core/test/fixtures/jellyfin/media_segments.json

@@ -0,0 +1,27 @@
+{
+ "Items": [
+  {
+   "Id": "5d1f0a7c2b3e4f60a1b2c3d4e5f60718",
+   "ItemId": "b18826be994070a79f9b52bc0f66f052",
+   "Type": "Outro",
+   "StartTicks": 12900000000,
+   "EndTicks": 13800000000
+  },
+  {
+   "Id": "0c9a8b7d6e5f40312a3b4c5d6e7f8091",
+   "ItemId": "b18826be994070a79f9b52bc0f66f052",
+   "Type": "Intro",
+   "StartTicks": 300000000,
+   "EndTicks": 1200000000
+  },
+  {
+   "Id": "1a2b3c4d5e6f47089a0b1c2d3e4f5061",
+   "ItemId": "b18826be994070a79f9b52bc0f66f052",
+   "Type": "Preview",
+   "StartTicks": 13800000000,
+   "EndTicks": 14100000000
+  }
+ ],
+ "TotalRecordCount": 3,
+ "StartIndex": 0
+}

packages/core/test/jellyfin_client_test.dart

@@ -272,6 +272,38 @@ void main() {
     });
   });
 
+  group('media segments', () {
+    // Shape from Jellyfin's MediaSegmentDto (the live 10.11 server answers
+    // 200 with an empty list: no segment provider installed).
+    test('parses and sorts the ranges by start', () async {
+      http.on('GET', '/MediaSegments/b18826be994070a79f9b52bc0f66f052', fixture: 'media_segments');
+      final s = await client.mediaSegments('b18826be994070a79f9b52bc0f66f052');
+      expect(http.last.method, 'GET');
+      expect(s.map((e) => e.type), [
+        JellyfinSegmentType.intro,
+        JellyfinSegmentType.outro,
+        JellyfinSegmentType.preview,
+      ]);
+      expect((s.first.start, s.first.end), (const Duration(seconds: 30), const Duration(minutes: 2)));
+      expect(s[1].start, const Duration(minutes: 21, seconds: 30));
+      expect(s.first.itemId, 'b18826be994070a79f9b52bc0f66f052');
+    });
+
+    test('empty list, and none on servers without the endpoint', () async {
+      http.on('GET', '/MediaSegments/a', body: '{"Items":[],"TotalRecordCount":0,"StartIndex":0}');
+      expect(await client.mediaSegments('a'), isEmpty);
+      expect(await client.mediaSegments('missing'), isEmpty); // 404
+      http.on('GET', '/MediaSegments/x', status: 401);
+      await expectLater(client.mediaSegments('x'),
+          throwsA(isA<JellyfinException>().having((e) => e.isUnauthorized, 'unauthorized', true)));
+    });
+
+    test('unknown types stay unknown', () {
+      expect(JellyfinSegmentType.parse('Something'), JellyfinSegmentType.unknown);
+      expect(JellyfinSegmentType.parse(null), JellyfinSegmentType.unknown);
+    });
+  });
+
   group('playback', () {
     test('playbackInfo asks for direct play and parses the session', () async {
       http.on('POST', '/Items/b18826be994070a79f9b52bc0f66f052/PlaybackInfo', fixture: 'playback_info');

packages/core/test/jellyfin_live_test.dart

@@ -113,6 +113,12 @@ void main() {
     final src = pi.primarySource!;
     expect(src.supportsDirectPlay, isTrue);
 
+    // 10.10+: the endpoint answers (often an empty list: segments need a
+    // provider plugin); ranges are well formed when present.
+    for (final seg in await client.mediaSegments(eps.first.id)) {
+      expect(seg.end, greaterThan(seg.start));
+    }
+
     final http = HttpClient();
     addTearDown(() => http.close(force: true));
     final req = await http.getUrl(client.streamUrl(eps.first.id, mediaSourceId: src.id));